The invention relates to a water-carbonizing system in a preferably cooled, pressure tank into which water (up to a predetermined level) and CO.sub.2 gas (by means of a pressure-reducing valve assembly and a supply line) are introduced as required, and from which the carbonized water is drawn off by means of a closing and pressure-reducing valve.
This type of water-carbonizing system is particularly applied to beverage dispensers in which carbonized water is mixed with beverage concentrates to prepare a beverage that is ready for consumption. To do this, a storage tank is used in which water is enriched with CO.sub.2 gas and cooled. In order to ensure a sufficient carbonization of the water, it is necessary, or at least advisable, to carry out the carbonization in the storage tank under high pressure. Toward this end, water is introduced into the storage tank, as required, by means of a liquid-level-dependent unit controlling the quantities of water to be. Also, CO.sub.2 gas is introduced by means of a pressure-dependent unit controlling the quantities of gas to be moved. The unit controlling the quantities of water to be moved may be either a pump unit, a control valve if an assured water supply is available subjected to a sufficiently high pressure, or a combination of both. Ordinarily, the unit for controlling the quantities of CO.sub.2 gas to be moved is a self-regulating, pressure-reducing valve. Pressure-reducing valves of known construction are able to provide a relatively constant preset gas pressure, provided a higher gas pressure is applied to the inlet side.
Special problems arise in these systems when the storage tank has to be filled anew with water and/or CO.sub.2 gas in a volume above the usual intermittent mode of operation. Specifically, when the supply in the CO.sub.2 storage cylinder is exhausted and it is necessary to replace this storage cylinder, a pressure drop is present or imminent in the storage tank. This pressure drop leads to an insufficient carbonization of the water. It may also be advisable to provide a pressure drop in the storage tank that will allow maintenance work to be carried out or a malfunction to be remedied under normal atmospheric pressure.